a-a a-b aaa aab aad aaf aan aar ab- aba abb abd abf abn abr ad- ada adb add adf adn adr af- afa afb afd aff afn afr an- ana anb and anf ann anr ar- ara arb ard arf arn arr baa bab bad baf ban bar bba bbb bbd bbf bbn bbr bda bdb bdd bdf bdr bfa bfb bfd bff bfn bfr bna bnb bnd bnf bnn bnr bra brb brd brf brn brr daa dab dad daf dan dar dba dbb dbd dbf dbn dbr dda ddb ddd ddf ddn ddr dfa dfb dfd dff dfn dfr dna dnb dnd dnf dnn dnr dra drb drd drn drr faa fab fad faf fan far fba fbb fbd fbf fbn fbr fda fdb fdd fdf fdn fdr ffa ffd fff ffn ffr fna fnb fnd fnf fnn fnr fra frb frd frf frn frr naa nab nad naf nan nar nba nbb nbd nbf nbn nbr nda ndb ndd ndf ndn ndr nfa nfb nfd nff nfn nfr nna nnb nnf nnn nra nrb nrd nrf nrn nrr ra- raa rab rad raf ran rar rba rbb rbd rbf rbn rbr rda rdb rdd rdf rdn rdr rfa rfb rfd rff rfn rfr rna rnb rnd rnn rnr rra rrb rrd rrf rrn rrr